When pelletizing or sintering plants the bulk material to be treated, for example iron ore or zinc ore, is loaded onto a pallet car where a plurality of cars forms an endless chain, also referred to as traveling grate. The pallet cars are filled with the bulk material and pass through various treatment stations, in which a thermal treatment of the material, such as drying, firing and cooling, is effected. By a drive or lifting wheel, the pallet car chain is moved through the treatment stations along a top strand of a guide rail by a means described below. Pallet cars include a track assembly comprising a set of track rollers that rotatably support the pallet cars and are configured to be guided in the rails and a set of pressure roller bearings which are adjacent to the track rollers. At the end of the top strand, the heat-treated material is dumped by gravity at a lowering wheel or tipping wheel (discharge station), whereupon the empty pallet cars are returned upside down along a bottom strand to the lifting wheel. Tooth gaps of the drive or lifting wheels engage pressure roller bearings which are arranged on the axle and adjacent to the track rollers which serve to lift the pallet cars from the bottom strand to the top strand and return the pallet cars to an upright position. Accordingly, the pallet car chain is moved in the top strand and the bottom strand by the pushing and pulling action of the drive and driven wheels on the pressure roller bearings.
Roller bearings, which are a type of bearing, carry a load by placing rolling members (such as balls or rollers) between two bearing rings called races. Roller bearings are known to be used in many types of industries for power transmission, in gear pumps, and in machine tools. Pressure roller bearings are a type of roller bearings and distinct from typical roller bearings, pressure roller bearings are designed with additional considerations in mind. Pressure roller bearings have to support the heavy loads carried by the pallet cars. Pressure roller bearings are also subjected to severe and constant mechanical stresses when they continuously engage and disengage from the tooth gaps of the lifting and lowering wheels during use. Accordingly, pressure roller bearings are generally robustly built and designed to withstand significant mechanical stresses. However, current designs of pressure roller bearings, which are substantially cylindrical, have been found to be fairly susceptible to breakage.
Consequently, pallet cars must be exchanged after a certain period of use, and during the repair of the pressure roller bearings, the sintering process may be slowed or even halted. To minimize the disruption of the sintering plant, some systems are known for efficiently replacing damaged pallet cars to effect repairs to, among other things, the pressure roller bearings. US patent application 2014/0021016 to Schulakow-Klass discloses a device for changing a damaged pallet car. Using the system of the Schulakow-Klass, an individual damaged pallet car can more easily be separated from the travelling grate for effecting the necessary repairs. Nonetheless, during the repair process, the particular pallet car itself is still not usable.
Accordingly, there is a need for a pressure roller bearing that is more durable and less susceptible to breakage.
Downtime of the sintering plant is unavoidable and costly when the drive or driven wheels are damaged such that they are rendered inoperable. Maintaining operational drive or driven wheels is of paramount importance, and can come at the expense of the pressure roller bearings which can be sacrificed to maintain the operation of the drive or driven wheels since the costs and effort to repair and/or replace the drive or driven wheels is considerably greater than the costs to replace pressure roller bearings. The damage to the drive or driven wheels occurs at the mating points of the tooth gap of the drive or driven wheel with the pressure roller bearings.
The loading of the conventional cylindrical pressure roller bearing on the drive and driven wheel causes the tooth gaps to wear out and/or break. When this occurs, the entire drive or lifting wheel or at least the damaged tooth gap segment which may be removably bolted onto the drive and driven wheels, must be replaced, or at least repaired, which is a time consuming and expensive task. During this time, the entire sintering process may come to a halt.
Accordingly, there is a need for an improved pressure roller bearing that not only resists wear, but also minimizes damage caused to the tooth gaps of the drive and driven wheel as a consequence of the severe and constant engagement with the pressure roller bearings of the pallet car.